Hmmm, last I heard( and mine you, I aged out two years ago so things "could" have changed), the standard size to a bassline in corps is 18, 20, 24, 28, 32. Some corps opt for a 22/26 in the middle and even a 30 at bottom but other then that basses are a great size.
Now I know they arent like old days where top bass was a 24" drum, but.....more musicality has to be thought of now a days with basslines being given a number of melodic lines and motifs.
And to agree with which Scribetoo, open your ears and you'll hear plenty of bass notes. I can go down a list of moments in a show(s) from previous years where the bassline was more then presence in the music.
Listen to Cavies 04 for instances......